Mark 4:18-19
And these are they which are sown among thorns; such as hear the word, And the cares of this world, and the deceitfulness of riches, and the lusts of other things entering in, choke the word, and it becometh unfruitful.
Jesus gives the secret to keeping the excitement of serving God so that you can continue to be fruitful. Certainly, every believer should desire to be fruitful as a believer. In fact, if you don't have that desire, you have already fallen for Christ’s warning that would cause a believer to become unfruitful.
There is a critical phrase in these verses that show how a person becomes unfruitful, and that phrase is, it becometh unfruitful. This person doesn't immediately stop being fruitful, but they slowly become unfruitful. They didn't wake up one day and say that they would stop bearing fruit, but they slowly stopped producing fruit because they slowly let something else take the fervor of trying to bear fruit away.
When I moved into my present home, there was a plumb tree in my backyard. That plumb tree produced plumbs the first year in our house. One year, I noticed the tree produced fewer plumbs than it did the year before. I didn't think much about it. The next year there were hardly any plumbs on the tree. The next year I had to cut off one main part of the tree that had died. This tree finally died. How did this tree die? It died because something slowly started eating away at the tree that caused that tree to no longer bear fruit. That tree is worthless because it has no fruit; it is dead.
Many believers slowly become unfruitful for one reason: they become entangled with the cares of this life. You will notice that Jesus says the cares of this world and the deceitfulness of riches is what causes one to become unfruitful. This is why God says in Galatians 5:1, Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage. God also warns in 2 Timothy 2:4, No man that warreth entangleth himself with the affairs of this life; that he may please him who hath chosen him to be a soldier. You slowly become unfruitful because you entangle yourself with the cares of life and the deceitfulness of riches.
The word entangleth means to slowly intertwine the cares of the world and the deceitfulness of riches into your life. What happens is you add one care of the world a little bit at a time into your life. You don't do this quickly, but you do it gradually. Those cares become demanding on your life and pull you away from what you are supposed to be as a believer. Because you are pulled away from what you are supposed to do, you slowly stop bearing fruit as you used to do until one day you are as dead as the tree in my backyard.
My friend, many churches have stopped bearing fruit because they became entangled in the unimportant cares of the world. Many preachers have lost their fire because they got entangled in life’s affairs instead of continuing to go after the souls of man. Other things start becoming more important than soul winning, and before long you are entangled in the affairs of this life and not in bearing fruit.
Nobody starts out saying they will become unfruitful; they just slowly become unfruitful until they are spiritually dead. If you don't want to become unfruitful, only let your life be entangled in the work of the LORD, and you will never find yourself being choked by the cares and riches of this world.